1,720,989 research outputs found
Experiments and qualitative analysis by artificial neural network approach on pool boiling of FC-72 on finned surfaces confined by an unheated horizontal wall
No full textHeat transfer measurements were taken during nucleate pool boiling of FC-72 (a saturated liquid utilized for thermal control of electronic components) from extended finned surfaces placed in a horizontal channel. The influence of channel width on boiling behavior for various extended finned surfaces was experimentally investigated. These finned surfaces have an array of uniformly or non-uniformly spaced straight spines with a square cross-section. The fins had a length of 3 mm or 6 mm. Starting from a uniform configuration, for which the width spacing of the spines was 0.4 mm, non-uniform surfaces were obtained by regularly removing some rows of spines. The effects of channel width (0.5 - 20 mm) and spines distribution were analyzed. The case of an extended unconfined surface was investigated and used as a reference to compare the effect of the confinement. An Artificial Neural Network (ANN) with one hidden layer was trained with the experimental data to predict the heat flux. An optimization algorithm was implemented to calculate the geometry that maximizes the predicted heat flux operating near the maximum temperature limit under different constrictions as fixed fin height or fixed channel width
A systematic literature review on Lattice Boltzmann Method applied to acoustics
No full textThe Lattice Boltzmann Method (LBM) can be applied to several fluid dynamic problems in the time domain. This numerical method indirectly solves the Navier–Stokes equations in a weakly compressible limit that allows acoustic wave propagation. This work presents a systematic literature review concerning the application of the LBM in acoustics. Applications found in the literature are classified and presented in different categories, including wave theory, boundary conditions, sound absorption materials, aeroacoustics, and musical acoustics. The increasing amount of research in recent years about aeroacoustics is remarkable, thanks to the intrinsically coupled treatment of the acoustical field and the mean flow, the potential of studying different wave phenomena such as diffraction and scattering, the easy way to model complex geometric boundaries in 2D and 3D, and finally thanks to the increasing available computational power. Some examples were included to illustrate the LBM capabilities to simulate sound wave phenomena, including point source modeling, diffraction and interference of sound waves, jet noise, and edge noise. This work will give a retrospective of the research developed in the past and a perspective on how this numerical method might evolve in the acoustical field
Experiments in natural circulation: influence of scale factor on the stability behaviour
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System codes capabilities in predicting instabilities in single phase natural circulation
No full textParallel connected natural circulation loops using different working fluids: experimental results
No full textNatural Circulation Loops (NCLs) are closed-loop systems that transport heat from a source to a heat sink without a pump, relying on free convection of the working fluid. Previous research has focused on the stability and influence of different operative parameters on NCLs. This experimental study investigates the thermo- hydraulic performance of three parallel-connected NCLs with small inner diameters using three different working fluids: deionized water, glycol aqueous solution (50+50% wt), and FC-43 dielectric fluid. This study examines the steady-state behaviour of the NCLs at various heat sink temperatures and heat powers. The results indicate that the common one-dimensional model for a single loop's steady-state can be applied to this configuration and for all the tested fluids, and a proposed figure of merit can describe the working fluids and predict their steady-state behaviour
Thermo-hydraulic performance of connected single-phase natural circulation loops characterized by two different inner diameters
No full textIn this paper, an experimental study regarding the natural circulation in connected vertical rectangular loops is presented. Typically, the geometry of the natural circulation loops (NCL) is rectangular or toroidal and the analysis is focused on the thermo-hydraulic behaviour of a single working loop. In this study, a new approach referred to several NCLs simultaneously operated was investigated. In the experimental setup, the lower heated sections of the NCLs are connected. The tests were carried out by varying the internal diameter of the loops to investigate the influence of the mutual interaction between two adjacent NCLs. The data were analyzed by the modified Vijayan's correlation showing a good agreement. A simple relationship is proposed to normalize the data both in terms of inner tube diameter and heat sink temperature. The results obtained with two NCLs characterized by different internal diameters could be considered as the first attempt to try optimizing several connected NCLs
Application of Cathare v1.3u and Relap5/mod3.2 codes to a rectangular natural circulation loop
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